改善太平洋鐵木心材水溶性抽出物釋出之方法及其處理材之耐久性

Abstract

本研究為了解決太平洋鐵木（Intsia palembanica）心材利用時深紅色水溶性抽出物易釋出而污染環境的問題，乃將太平洋鐵木心材於常溫低壓下含浸不同的金屬離子，使金屬離子與水溶性抽出物反應形成穩定的螯合物。試驗結果顯示，FeCl2及CuCl2能抑制水溶性抽出物釋出之效果最佳，且100°C乾燥溫度可增強處理材之抗流失性，又以CuCl2改善效果最為顯著。0.1% FeCl2及CuCl2處理材於100°C加熱後，材色分別為黑褐色及紅褐色，由16-day淋洗試驗之結果得知，試材重量損失率由未處理材的13.2%分別降為1.6%及1.7%，且藥劑固著性佳，實為有效抑制太平洋鐵木心材水溶性抽出物釋出且環境較友善之方法。 以核磁共振光譜儀分析太平洋鐵木心材水溶性抽出物得知，其主要由縮合單寧所組成，且B環上含鄰二羥基，此為抽出物與金屬離子反應之關鍵結構。另使用紅外線光譜儀分析水溶性抽出物與FeCl2或CuCl2之反應物得知，於室溫下Fe離子與抽出物反應較強，可形成大量水不溶之螯合物，而加熱則會促進Cu離子氧化抽出物，形成半鄰醌類及鄰醌類化合物，進而增加Cu離子與抽出物之螯合反應；另由0.1% FeCl2及CuCl2處理材之紅外光光譜得知，金屬離子主要與抽出物反應。 進一步評估0.1% FeCl2及CuCl2處理材之耐光性、耐腐朽性及尺寸安定性得知，水溶性抽出物可緩和太平洋鐵木心材木質素之光劣化，故0.1% FeCl2及CuCl2處理材具有優異之耐光性，照光後材色變化較小；另外，移除水溶性抽出物雖然不會影響其耐腐朽性質，但水溶性抽出物可加強CuCl2之固著，進而抑制腐朽菌的降解；0.1% FeCl2及CuCl2處理材之表面較具疏水性，於高溼環境下平衡含水率較低，且體積膨脹較緩慢。因此，0.1% FeCl2及CuCl2之處理除了能有效抑制太平洋鐵木心材水溶性抽出物釋出之外，亦可延長太平洋鐵木心材產品於戶外應用之生命週期，且不會污染環境。

The dark-red aqueous extracts (AEs) of merbau (Intsia palembanica) heartwoods would be easily leached out and cause a contaminant in the adjacent areas. The main purpose of this study was to exploit appropriate treatments to avoid the environmental impact of AEs leaching. Several metal compounds were impregnated into merbau heartwoods at ambient temperature under vacuum. The AEs can act as chelators and form stable and water-insoluble complexes with metal ions, thereby solving the extract-stain problems of merbau heartwoods. The results revealed that FeCl2 and CuCl2 are effective reagents for inhibiting the release of AEs. In addition, drying at 100°C could increase the bleed resistance of treated wood, especially in the CuCl2 case. The appearances of 0.1% FeCl2- and CuCl2-treated woods dried at 100°C were dark-brown and red-brown, respectively. Their weight losses were only 1.6% and 1.7%, respectively, compared to 13.2% for untreated wood after 16-day leaching test. These two treatments also have good fixation of metals, and consequently are relatively environmentally-benign and efficient approaches to inhibiting the release AEs of merbau heartwood. Results from nuclear magnetic resonance spectra revealed that AEs were mainly composed of condensed tannins with an o-dihydroxyl group in the B ring, which was an indispensable group to complex metal ion. Infrared spectroscopy was further employed to analyze the products after AEs reacted with FeCl2 or CuCl2 in water. The results implied that FeCl2 had stronger reactivity to the AEs than that of CuCl2 at ambient temperature; on the other hand, CuCl2 could catalyze the AEs to form quinones or o-semiquinones by means of heat, and consequently induced the chelating reaction between the quinones and copper ion. Besides, the IR spectra of 0.1% FeCl2- and CuCl2-treated woods revealed that the majority of metal ions reacts with extracts. Furthermore, the durability of 0.1% FeCl2- and CuCl2-treated woods was also examined in this study. Results from lightfastness test demonstrated that AEs present in merbau heartwood can prevent the photodegradation of lignin and be slight color changes of treated specimens after irradiation. Even though removing AEs was no effect on the durability of merbau heartwood, the copper ion was still fixed within specimens by AEs, and consequently their resistance against decay fungi were enhanced. Moreover, 0.1% FeCl2- and CuCl2-treated specimens with hydrophobic surfaces have the lower equilibrium moisture content and slower swelling than unrtreated. Therefore, merbau heartwood treated with 0.1% FeCl2 and CuCl2 can solve the AEs leacing problem by environmentally-benign way, meanwhile provide longer product life cycle of merbau heartwood for exterior applications.